RF measurements, antennas and link-budget assumptions
Separate absolute power and ratios
A dB value expresses a logarithmic ratio, while dBm expresses power referenced to one milliwatt. Antenna gain stated in dBi uses an isotropic reference and is not itself an absolute transmitter output. In a supplied simple model, ten dBm corresponds to ten milliwatts and twenty dBm to one hundred milliwatts. Adding ten dB to a power level multiplies its corresponding linear power by ten. Use the stated reference and unit before comparing measurements; a negative received dBm value is not a negative physical power.
Follow both sides of the link
A simplified link budget combines transmit power, antenna gains, cable/connector losses and propagation loss under stated assumptions. EIRP concerns the relevant radiated-power model and does not replace receiver sensitivity or local regulatory review. An AP may be heard by a client that cannot send a usable return signal. Increasing AP output alone can therefore enlarge the visible cell without creating a balanced usable link. Antenna pattern, orientation, polarization and the actual device installation affect the result.
Interpret propagation as a model
Free-space loss is an idealized relationship, not a complete indoor prediction. Materials, reflections, absorption, diffraction and interference can change actual performance. A fixed attenuation number for every drywall, concrete wall or human body is not a universal constant. Higher nominal gain redistributes radiation rather than creates energy; a directional antenna can reduce coverage elsewhere. Frequency, channel bandwidth, noise and receiver capability matter alongside distance. Regulatory band and power permissions depend on actual jurisdiction and device approvals.
Compare signal, noise and performance
RSSI, noise-floor estimates and signal-to-noise calculations require the instrument’s stated measurement meaning. In a supplied logarithmic model with received signal minus sixty-five dBm and noise minus ninety dBm, the difference is twenty-five dB. That arithmetic does not establish a universal acceptance threshold. Validate actual modulation/rate behavior, retransmissions, application demand and client capability under representative conditions. A good received signal does not prove sufficient airtime capacity, correct authentication or usable application service. These exercises make no transmission, site survey or equipment adjustment and do not replace supported RF measurement, jurisdiction-specific rules or practical field skill.